Adding keyboard shortcut to a blender script
It would be better(and probably easier) to do this directly rather than using trying to use the keyboard shortcuts in the code. Try this:

seqs = bpy.context.scene.sequence_editor.sequences_all
for seq in seqs:
    seq.frame_final_duration = 10


Or if you want to just modify selected strips:

seqs = bpy.context.scene.sequence_editor.sequences_all
for seq in seqs:
    if seq.select:
        seq.frame_final_duration = 10


Or if you want to just modify the strips based in their length:

seqs = bpy.context.scene.sequence_editor.sequences_all
for seq in seqs:
    if seq.frame_final_duration == 1:
        seq.frame_final_duration = 10